CODEWITHSUNDEEP
dartffi
Michael Kanzieper
Michael Kanzieper

Reputation: 889

Is it possible to use a dart function as a callback function in C?

Is it possible, using ffi, to pass a pointer to the of dart function into a C module (i.e., to the * .so library) and access this dart function directly from the * .so library and use it by means call back?

Upvotes: 3

Views: 2045

Answers (2)

Samir N Ahmad
Samir N Ahmad

Reputation: 625

This is now possible using the NativeCallable class.

Here is an example

Upvotes: 3

Michael Kanzieper
Michael Kanzieper

Reputation: 889

Thank you very much for the information. This is what I need.

dart:

int myPlus(int a, int b) {
  print("dart.myPlus.a=$a,b=$b. $a+$b => ${a + b}");
  return a + b;
}

main() {
  ...   
  ffi.Pointer<ffi.NativeFunction<NativeIntptrBinOp>>
    pointer = ffi.Pointer.fromFunction(myPlus, 0);
  print(pointer);

  ffi.Pointer<ffi.NativeFunction<NativeApplyTo42And74Type>>
    p17 = dylib.lookup("ApplyTo42And74");
  ApplyTo42And74Type applyTo42And74 = p17.asFunction();
  int result = applyTo42And74(pointer);
  print("result => $result");
}

c:

#include <stdio.h>
#include <stdint.h>

typedef intptr_t (*IntptrBinOp)(intptr_t a, intptr_t b);

intptr_t ApplyTo42And74(IntptrBinOp binop) {
  printf("ApplyTo42And74()\n");
  intptr_t retval = binop(42, 74);
  printf("returning %lu\n", retval);
  return retval;
}

result:

Pointer<NativeFunction<(IntPtr, IntPtr) => IntPtr>>: address=0x7fb4acd98000
ApplyTo42And74()
dart.myPlus.a=42,b=74. 42+74 => 116
returning 116
result => 116

Upvotes: 6

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